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SULPHUR                                       113

length of the tube to the 100 mark is 175 mm., that of the straight tube from
the 10 mark to the 100 is 154 mm., and the bore of the tube 12-68 mm.

Into this tube are introduced 5 grams of the sulphur (which should be
passed through a sieve of i mm. mesh) and about ;one-half of the ether neces-
sary for the determination, this being absolutely anhydrous and alcohol-free,
D  0-719 at 15. By gentle tapping the air is completely displaced, more
ether being then added to about i cm. beyond the 100 mark. The apparatus
is placed in a water-bath kept exactly at 17-5 ; after some time the tube
is shaken vigorously for 30 seconds and returned to the bath, note being
made of the scale-division reached by the sulphur suspended in the ethereal
liquid : this division represents the degree of fineness of the sample. If the
temperature is 2 above or below 17-5, the result is raised or lowered by i
degree of fineness and the necessary correction must be made.

The result of the first agitation is too high, so that the determination is
repeated several times. After the second or third shaking, the results
usually differ by not more than 2 and the mean of two concordant results
is taken. Greater certainty is attained by carrying out the test in duplicate.

4. Sublimed Sulphur (Flowers of Sulphur)

This form of refined sulphur is in yellow powder composed mostly of
agglomerated, microscopic globules mixed with rhombic crystals (ground
sulphur being composed solely of crystals or crystalline fragments). It is
not completely soluble in carbon disulphide (thus differing from ground sul-
phur), at least 12% and, in fresh samples, sometimes more than 30%
remaining undissolved. When it is moistened with water, the latter may
become acid owing to the presence of traces of sulphuric acid.

With sublimed sulphur for agricultural purposes, the residue on cal-
cination and the degree of fineness (see Refined Sulphur) are determined ;
if for pharmaceutical purposes, arsenic is tested for.

Detection of Arsenic.^-2 grams are digested for 24 hours with 5 c.c.
of 10% ammonia and the solution filtered, acidified with hydrochloric acid
and saturated with hydrogen sulphide : in presence of arsenic the liquid
becomes yellow.

5. Magister of Sulphur (Precipitated Sulphur)

Pale yellow, almost colourless, insipid, impalpable powder. The tests
to be made are : residue on calcination, which should be inappreciable ;
treatment with dilute hydrochloric acid, which should not cause efferves-
cence, while the- filtered liquid should not be rendered turbid by sodium
carbonate (alkaline-earth carbonates) ; digestion with water, which should
not become acid ; test for arsenic (see Sublimed Sulphur).

6. Coppered Sulphur

In this product the copper sulphate is determined by repeatedly agita-
ting 10 grams with 200-250 c.c. of hot, acidified water, filtering, washing
with boiling water and estimating the copper by one of the methods given
under "Copper Sulphate."
A.C.                                                                                              b, the latter washed with hot water, dried, ashed and weighed.